Research On The Effect Of Steel-Resin Twisted Basalt Fiber On The Properties Of UHPC

Ultra High Performance Concrete(UHPC)is a high-strength and durable cement-based composite material.UHPC adopts the theory of particle tight packing to achieve the effect of reducing porosity and improving strength.UHPC is often used in steel bridge deck pavement,explosion-proof structures,and thin-walled structures.However,the high brittleness of UHPC affects its widespread application.The addition of steel fibers(SF)can effectively increase the ductility,strength,and fracture energy of UHPC.However,SF has defects such as poor dispersibility,large self weight,and susceptibility to corrosion.Resin twisted basalt fiber(BF)has advantages such as strong anchoring effect and good dispersibility due to its unique ribbed surface shape.This article studies the effects of different fibers(SF,BF)and their dosages on the working performance,mechanical properties,durability,and interlayer bonding performance of UHPC,which is of great significance for the study of the influence of hybrid fibers in UHPC.Firstly,the effect of single doped fibers on the working and mechanical properties of UHPC was studied.The dosage is 0.25%,0.5%,0.75%,1.0%,1.5%,and 2.0%.The results show that BF has a significant impact on the flowability of UHPC.With the increase of BF content,the compressive bending strength and splitting tensile strength of UHPC first increase and then decrease,with the optimal dosage of 1.0%.At low dosage,the flexural strength of BFUHPC is better than that of SFUHPC.SF has a significant impact on the toughness of UHPC,but high dosage of SF has a smaller effect on the strength improvement of UHPC,and even a decrease in splitting tensile strength.Secondly,by partially replacing SF with BF,the working and mechanical properties of hybrid fiber UHPC were studied,with substitution rates of 25%,50%,and 75%.The results show that with the increase of BF substitution rate,the compressive strength of UHPC gradually decreases,while the flexural strength,splitting tensile strength,and fracture energy first increase and then decrease.The optimal dosage is 0.5%BF+1.5%SF.Combined with SEM electron microscopy scanning,the hydration products of hybrid fiber UHPC are generated more,and the microstructure is denser.Finally,the durability and interlayer bonding performance of hybrid fiber UHPC with SMA were studied.The impact resistance of UHPC was tested using impact tests.The durability of hybrid fiber UHPC was studied through dry shrinkage tests,freeze-thaw cycling tests,and water absorption tests.The bonding performance of UHPC with SMA was studied using interlayer pull-out and oblique shear tests.The results show that the addition of an appropriate amount of BF can improve the impact resistance of UHPC,reduce the dry shrinkage of hybrid fibers,and improve their frost resistance.The addition of BF reduces porosity and refines pore size,resulting in smaller water absorption of the specimen.The bonding performance between UHPC and SMA is good,making it suitable for bridge structures.This article selects BF and SF hybrid fibers,with a total volume content of 2%.Through comprehensive exploration of their working performance,mechanical performance,durability,and interlayer bonding performance,the mechanism of hybrid fibers on UHPC is proposed,and the optimal fiber combination is proposed to provide data support for the engineering application of UHPC.